/**
 * Created with IntelliJ IDEA.
 * Description:给你一个链表的头节点 head ，判断链表中是否有环。
 * User: wangxin
 * Date: 2025-04-14
 * Time: 21:20
 */

class ListNode {
      int val;
      ListNode next;
      ListNode(int x) {
          val = x;
          next = null;
      }
  }
public class Test {
    public boolean hasCycle(ListNode head) {
        if(head == null||head.next == null){
            return false;
        }
        ListNode slow = head;
        ListNode fast = head.next;
        while(slow !=fast){
            if(fast == null||fast.next == null){
                return false;
            }
            slow = slow.next;
            fast = fast.next.next;
        }
        return true;
    }
}
